1. Field of the Invention
The present invention is directed to a storage apparatus, and in particular, to a stand-alone or add-on shelving unit that can be positioned on an existing support structure such as an existing shelf to provide additional storage space. In a first embodiment, the shelving unit is configured to engage and lock to the existing support structure. In a second embodiment, the shelving unit is configured to be expandable.
2. Description of Related Art
There are a variety of stand-alone or add-on shelves designed to be positioned on an existing shelf for increasing the storage capacity of the shelf. One such type of stand-alone shelf simply includes vertical legs that are supported by an existing shelf and a horizontal shelf surface extending between the legs. While this type of shelf presents an additional surface on which items may be stored, it may slide or move with respect to the existing shelf when items are placed on or removed from it. In order to prevent sliding, another type of add-on shelf includes a clamping structure that engages the existing shelf. This shelf, however, includes structure positioned between the existing shelf and the horizontal shelf surface of the add-on shelf that substantially prevents items from being placed on the existing shelf beneath the horizontal surface, and therefore the overall storage capacity of the existing shelf is reduced.
There are also width adjustable shelves that are supported by an existing shelf for increasing its storage capacity. One type of width adjustable shelf includes two sections that slide with respect to each other for altering the width of the shelf. The shelf includes six legs, one at each of the four corners of the shelf and two that support the middle of the shelf. The middle legs may interfere with storing items on the existing shelf beneath the width adjustable shelf. Another type of width adjustable shelf has two sections that are operable to engage each other in a plurality of width adjustable positions. Each section has a shelf surface joined to a vertical leg that is supported by an existing shelf. The shelf surfaces engage each other in each of the width adjustable positions via structures that extend above the horizontal plane of the shelf surfaces. The structures extending above the horizontal plane may interfere with storing and removing items placed on the shelf surface. While the prior art stand-alone or add-on shelving units are useful, a need remains in the art for stand-alone or add-on shelving units that can be effectively utilized to enhance storage in any area in the home or office.